I did the same for an in-between-upgrade. I wanted to squeeze another year out my AGP NVIDIA card, so I went with a L775 socket mobo that still supported the AGP slot, but allowed me to go dual core on a Pentium. I went with TigerDirect's end of summer special and got a good combo deal on cpu & mobo, which after rebate only ran me about $145. In another year, I'll make the major upgrade and go PCI Express. I'm very happy with the upgrade I made from my aging P4 2.4 Ghz system, which is carrying on its good work in my daughter's case.
Robert